AB0929 CLINICALLY AMYOPATHIC DERMATOMYOSITIS (CADM) WITH ANTI–MELANOMA DIFFERENTIATION-ASSOCIATED GENE 5 ANTIBODY POSITIVE: UNDERSTANDING IT’S CLINICAL PRESENTATION AND EXTENT OF LUNG INVOLVEMENT
Authors: T. Mahadevan, K. L. Ng, M. H. Nordin, A. Mohamed Ismail
Journal: Annals of the Rheumatic Diseases (2023)

<h3>Background</h3> CADM is a subset of dermatomyositis with cutaneous manifestation in the absence of myositis. Myositis-specific autoantibodies (MSA) permits the delineation of homogenous subgroups of DM. CADM associated with anti-melanoma differentiation-associated gene-5 antibody positive (anti-MDA5+) is typically characterized by the presence of dermatomyositis (DM) skin rash and polyarthralgia and interstitial lung disease (ILD) <h3>Objectives</h3> To elaborate on clinical features and management of two patients presenting with MDA-5 positive CADM and associated interstitial lung disease. <h3>Methods</h3> Patient's clinical notes including laboratory results and images were reviewed. <h3>Results</h3> <b>First Case:</b> 59-year-old lady with underlying hypertension presented with inflammatory symmetrical polyarthritis associated with high rheumatoid factor value for 5 months duration. She was initially diagnosed as seropositive Rheumatoid arthritis and treated with T. Methotrexate 15mg/weekly. She achieved clinical remission within two months of treatment. However, eight months later, she developed progressive shortness of breath and reduce effort tolerance (MMRC III). Examination revealed palmar papules and periungual erythema on bilateral hands, and fine crepitations on lung auscultation. No proximal myopathy and active synovitis. ANA 1:1280 (speckled) and MSA panel revealed MDA-5positive.She was unable to perform the lung function test (weak blow) and high-resolution computed tomography (HRCT) showed fibrotic nonspecific interstitial pneumonia (NSIP). She was started on high dose prednisolone (1mg/kg) and oral cyclosporin 100mg daily. One month post treatment, her reduced effort tolerance improved (MMRC II). <b>Second Case:</b> 32-year-old lady presented with symmetrical arthritis of proximal interphalangeal joints for one year associated with diffuse erythematous rash over the face and neck for five months. She had one month history of steroid exposure. No associated proximal weakness or reduced effort tolerance. Examination revealed hyperpigmentation over the face and Gottron papule over bilateral hands. Auscultation of lung was clear and no synovitis was noted. ANA 1:80 (speckled) and MSA panel revealed MDA-5 positive. Lung function test was normal, however, high-resolution computed tomography (HRCT) revealed interstitial lung disease with organizing pneumonia. She was started on prednisolone 0.3mg/kg for her cutaneous manifestation. Assessment four months later, showed good effort tolerance and complete resolution of cutaneous manifestation. <h3>Conclusion</h3> Myositis-specific autoantibodies have been found to correlate with clinical features and have also served as a diagnostic and prognostic marker. We suggest all patients with MDA-5 positive to undergo CT imaging irrespective of their respiratory symptoms. <h3>Reference</h3> [1]Allenbach, Y., Uzunhan, Y., Toquet, S., Leroux, G., Gallay, L., Marquet, A., Meyer, A., Guillaud, C., Limal, N., Gagnadoux, F. and Hervier, B., 2020. Different phenotypes in dermatomyositis associated with anti-MDA5 antibody: study of 121 cases. <i>Neurology</i>, <i>95</i>(1), pp.e70-e78. <h3>Acknowledgements:</h3> NIL. <h3>Disclosure of Interests</h3> None Declared.